WASHINGTON - America's wild weather year has set another record: a dozen billion-dollar catastrophes.

The National Oceanic and Atmospheric Administration said Wednesday that it has recalculated the number of weather disasters passing the billion-dollar mark, with two new ones, pushing 2011's total to 12. The two costly additions are the Texas, New Mexico and Arizona wildfires and the mid-June tornadoes and severe weather.

NOAA uses $1 billion as a benchmark for the worst weather disasters. This year's total of a dozen billion-dollar calamities matches the number for all of the 1980s, even when the older figures are adjusted for inflation.

Extreme weather in America this year has killed more than 1,000 people, according to National Weather Service Director Jack Hayes. The dozen billion-dollar disasters alone add up to $52 billion in damage. Hayes, a meteorologist since 1970, said he has never seen a year for extreme weather like this, calling it "the deadly, destructive and relentless 2011."

And this year's total may not stop at 12. Officials are still adding up the damage from the Tropical Storm Lee and the pre-Halloween Northeast snowstorm, and so far they are both at the $750 million mark. And there's still nearly a month left in the year.

Scientists blame an unlucky combination of global warming and freak chance. They say even with the long-predicted increase in weather extremes triggered by manmade climate change, 2011 in the U.S. was wilder than they predicted. The six large outbreaks of twisters, which were especially deadly this year, can't be attributed to global warming, but increased droughts, heat waves and wildfires are expected to increase with global warming, scientists say. More people are also living in areas that are prone to disasters.

"The degree of devastation is extreme in and of itself and it would be tempting to say it's a sign of things to come, though we would be hard-pressed to see such a convergence of circumstances occurring in one single year again for a while," said Jerry Meehl, a climate scientist at the National Center for Atmospheric Research in Boulder, Colo.

The number of weather catastrophes that pass the billion-dollar mark when adjusted into constant dollars is increasing with each decade. In the 1980s, the country averaged slightly more than one a year. In the 1990s, the average was 3.8 a year. It jumped to 4.6 in the first decade of this century. And in the past two years, it's averaged 7.5.

The old record for most billion-dollar disasters before this year was 2008 with nine.

But this isn't just about numbers and records, it's about people, said NOAA Administrator Jane Lubchenco.

"Each of these events is a huge disaster for victims who experience them," Lubchenco said in an email to The Associated Press. "They are an unprecedented challenge for the nation."

This year's dozen billion-dollar disasters are:

- Wildfires in Texas, New Mexico, and Arizona from spring to fall. Losses are more than $1 billion, with at least five deaths.

- Hurricane Irene along most of the East Coast in August. Losses exceed $7.3 billion with at least 45 deaths.

- Flooding in the upper Midwest along the Missouri and Souris Rivers in the summer. Damage is more than $2 billion, with at least five deaths.

- Flooding on the Mississippi River in spring and summer. Losses are $3 billion to $4 billion with at least two deaths.

- Drought and heat wave in the southern Plains and Southwest from spring to fall. Losses are near $10 billion.

Tornadoes and severe storms in the Midwest and Southeast from June 18 to June 22. They caused more than $1.3 billion in damage and killed at least three people.

Twisters in the Midwest and Southeast May 22-27. These killed 177 people and caused more than $9.1 billion in damage.

Tornadoes in the Southeast and Ohio Valley April 25-28. These killed 321 people and caused more than $10.2 billion in damage.

Tornadoes in the Midwest and Southeast April 14-16. These killed 38 people and caused more than $2.1 billion in damage.

Tornadoes in the Southeast and Midwest April 8-11. These caused more than $2.2 billion in damage.

Tornadoes in the Midwest and Southeast April 4 and 5. These inflicted more than $2.8 billion in damage and killed nine people.

The Groundhog Day blizzard killed 36 people and caused damage greater than $1.8 billion.

Seth Borenstein

AP Science Writer

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